During oil and gas exploration conventional granulometry analysis is a time consuming, logistically complex procedure. It requires the transportation and storage of a large number of samples of the rock cuttings produced during drilling to the laboratory. Conventional practice is to have a field worker manually scoop a shovel full of the cuttings as they fall off of the shaker table (the part of the drilling rig which separates the rock cuttings from the drilling fluid so that the fluid can be reused). The sample shovel-full is poured into a canvas bag and transported from the well site (which is typically remotely located) to a laboratory. Conventionally, a series of tall, wide cylindrical containers are used to separate the cuttings by particle size and density. The sample is combined with water and poured into a container. At a predetermined interval the upper portion of the partially settled sample is siphoned off and allowed to settle in a second container. This procedure is repeated until the size of particle remaining in suspension is of a desired size. Next, all the containers are dried and weighed using an analytic balance. The quantity of specific grain sizes is tabulated for interpretation. It is impractical to perform conventional granularity analysis during modern high speed drilling. Consequently, various down hole logging tools are used in place of conventional granulometry analysis to assess Porosity and Permeability.
Exploration focuses on the productivity of a potential reservoir during the drilling of a well in an unconsolidated formation. Detailed rock sampling and a corresponding granulometry analysis are the most accurate and direct method for defining the potential production horizons. Granulometry properties provide the best information for estimating the Porosity and Permeability of a reservoir. Unfortunately, conventional granulometry is not used in the exploration of unconsolidated formations due to the logistical problems associated with it. Instead, Logging properties (which are determined using down-hole tools) are substituted for granulometry parameters when calculating Porosity and Permeability. This produces less accurate information about a potential production zone.
In the proposed Microgranulometry, the apparatus and the process solve all the problems of conventional granulometry and produce useful, accurate information. Microgranulometry produces direct quantitative measurements of the SHALE, SILT and SAND content of the formation sample.